1. Technical Field
The present invention relates to a zoom lens, and more particularly to, a zoom lens having a diffraction surface, and a device having the zoom lens as a photographing optical system such as a camera.
2. Description of the Related Art
Market of cameras used for security and the like is widened, and demands are also increased in various fields. Among the demands, high image quality and high magnification changeability are constantly desired by users, and occupy large weights. Therefore, in the zoom lens used as a photographing lens, implementation of high performance with high magnification changeability is required.
Herein, in terms of high performance, a configuration having a resolving power corresponding to imaging elements of at least one million to five million pixels over the entire zoom range is needed. In addition, it is considered that a magnification changing ratio of about ×16 is needed as the high magnification changeability.
In addition, it is preferable that aberrations be sufficiently corrected even in a near-infrared wavelength region so that photographing is available even in a dark state.
In addition, widening of an angle of view is preferred, and preferably, a half angle of view at a short focal end of a zoom lens is about 25 degrees or more.
In addition, large-diameter of a lens is preferred, and preferably, an F number at a short focal end (sometimes, referred to as “wide angle”) is 2.0 or less.
As an example, there is a zoom lens which is configured to include, in order from an object side toward an image side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a negative refractive power, and a fourth lens group having a positive refractive power and in which the first lens group has a diffraction surface.
However, there has been no zoom lens sufficiently satisfying user's demands for achieving a high angle of view and a small size with a high magnification changing ratio, an F number of 2.0 or less at the short focal end, and, particularly, small aberration in a near-infrared region.